CLOSURE OF THEORY OF BRITTLE FRACTURE APPLIED TO SOIL CEMENT

THE REVIEWERS HAVE SUGGESTED THAT IT IS NOT FEASIBLE TO APPLY FRACTURE MECHANICS CONCEPTS TO COMPLEX MATERIALS LIKE SOIL CEMENT. BY STUDYING THE VARIATION OF G SUB C ACCORDING TO SOIL TEXTURE, CLAY MINERAL PRESENT, TEMPERATURE, AND THE RATE OF LOADING, THE WRITER SHOWED, HOWEVER, THAT THE FRACTURE PARAMETERS G SUB C AND K SUB C ARE TRULY PHYSICAL PROPERTIES REFLECTING THE RESISTANCE OF THE MATERIAL TO FRACTURE. THE WRITER IS IN AGREEMENT WITH THE DISCUSSERS THAT THE GEOMETRY OF THE TEST SPECIMENS AND THE METHOD OF LOADING COULD INFLUENCE THE OBSERVED VALUES OF G SUB C AND K SUB C. FOR EXAMPLE, THE MEASUREMENT OF VALID PLANE STRAIN FRACTURE TOUGHNESS VALUES IS DEPENDENT ON USING A SPECIMEN WITH SUFFICIENT SIZE SO THAT THE PLASTIC ZONE AT THE CRACK TIP IS RELATIVELY SMALL WITH RESPECT TO THE OVERALL DIMENSIONS OF THE SPECIMEN. A RELATIVELY LARGE QUANTITY OF DATA IS AVAILABLE WHICH INDICATES THAT IN THE NOTCH BEND TEST THE SPECIMEN WIDTH SHOULD BE GREATER THAN 2.5 TIMES THE SQUARE OF THE FRACTURE TOUGHNESS-TO-YIELD STRENGTH RATIO. FURTHERMORE, THE WRITER REALIZES THAT THE COMPLIANCE TEST TECHNIQUES PERMIT THE DETERMINATION OF STRESS INTENSITY FACTORS DIRECTLY FROM A COMPARISON OF OVERALL LOAD-DEFLECTION CURVES FOR STRUCTURES CONTAINING CRACKS OR NOTCHES OF DIFFERENT SIZE. THE DICUSSERS POINT OUT THAT THE STRESS FIELD AHEAD OF A MOVING CRACK IS DIFFERENT FROM A STATIC STRESS FIELD CRACK. FOR CONDITIONS EXISTING PRIOR TO THE INITIAL DEVELOPMENT OF A DISCONTINUITY, THE PROBLEM IS ESSENTIALLY STATIC. THE SAME IS TRUE ONCE A STEADY STEADY-STATE VELOCITY FIELD IS ESTABLISHED. HOWEVER, FOR CONDITIONS EXISTING IN THE TIME SPAN FROM THE INITIATION OF MOTION TO THE EVOLUTION OF STEADY STATE, DUE CONSIDERATION MUST BE GIVEN TO THE DYNAMIC PROBLEM AND PROGRESSIVE FAILURE. CONCERNING THE MOVING CRACKS TO DATE ONLY VERY SIMPLE BOUNDARY CONDITIONS HAVE BEEN AMENABLE TO THEORETICAL CONSIDERATIONS. THUS, TO OBTAIN A PROCEDURE WITH SOME HOPE FOR SUCCESS IT IS NECESSARY TO LIMIT CONSIDERATIONS TO EQUILIBRIUM CONDITIONS. /AUTHOR/

  • Supplemental Notes:
    • Vol 97, No SM 9, PP 1341-1342, 1 REF
  • Publication Date: 1971-9

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Filing Info

  • Accession Number: 00233214
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Dec 20 1971 12:00AM